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INT-738 Added documentation for the delayer endpoint

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This commit is contained in:
Mark Fisher
2009-07-18 17:23:03 +00:00
parent cea730322e
commit 59c0fd0e8d
4 changed files with 71 additions and 2 deletions
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58
spring-integration-reference/src/delayer.xml Normal file
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@@ -0,0 +1,58 @@
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<chapter id="delayer">
<title>Delayer</title>
<section id="delayer-introduction">
<title>Introduction</title>
<para>
A Delayer is a simple endpoint that allows a Message flow to be delayed by a certain interval. When
a Message is delayed, the original sender will not block. Instead, the delayed Messages will be
scheduled with an instance of <interfacename>java.util.concurrent.ScheduledExecutorService</interfacename>
to be sent to the output channel after the delay has passed. This approach is scalable even for
rather long delays, since it does not result in a large number of blocked sender Threads. On the
contrary, in the typical case a thread pool will be used for the actual execution of releasing the
Messages. Below you will find several examples of configuring a Delayer.
</para>
</section>
<section id="delayer-namespace">
<title>The &lt;delayer&gt; Element</title>
<para>
The &lt;delayer&gt; element is used to delay the Message flow between two Message Channels.
As with the other endpoints, you can provide the "input-channel" and "output-channel" attributes,
but the delayer also requires at least the 'default-delay' attribute with the number of milliseconds
that each Message should be delayed.
<programlisting language="xml"><![CDATA[ <delayer input-channel="input" default-delay="3000" output-channel="output"/>]]></programlisting>
If you need per-Message determination of the delay, then you can also provide the name of a header
within the 'delay-header-name' attribute:
<programlisting language="xml"><![CDATA[ <delayer input-channel="input" output-channel="output"
default-delay="3000" delay-header-name="delay"/>]]></programlisting>
In the example above the 3 second delay would only apply in the case that the header value is
not present for a given inbound Message. If you only want to apply a delay to Messages that have
an explicit header value, then you can set the 'default-delay' to 0. For any Message that has a
delay of 0 (or less), the Message will be sent directly. In fact, if there is not a positive delay
value for a Message, it will be sent to the output channel on the calling Thread.
<tip>
The delay handler actually supports header values that represent an interval in milliseconds (any
Object whose <methodname>toString()</methodname> method produces a value that can be parsed into a
Long) as well as <classname>java.util.Date</classname> instances representing an absolute time.
In the former case, the milliseconds will be counted from the current time (e.g. a value of 5000
would delay the Message for at least 5 seconds from the time it is received by the Delayer). In
the latter case, with an actual Date instance, the Message will not be released until that Date
occurs. In either case, a value that equates to a non-positive delay, or a Date in the past, will
not result in any delay. Instead, it will be sent directly to the output channel in the original
sender's Thread.
</tip>
</para>
<para>
The default scheduler will have a thread pool of size 1. If you want to configure and provide a
different scheduler, you can provide the reference through the 'scheduler' attribute:
<programlisting language="xml"><![CDATA[ <delayer input-channel="input" output-channel="output"
default-delay="0" delay-header-name="delay"
scheduler="someScheduledExecutorService"/>]]></programlisting>
</para>
</section>
</chapter>

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spring-integration-reference/src/filter.xml
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@@ -2,7 +2,7 @@
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<chapter id="filter">
<title>Message Filter</title>
<title>Filter</title>
<section id="filter-introduction">
<title>Introduction</title>

10
spring-integration-reference/src/gateway.xml
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@@ -53,6 +53,16 @@
@Gateway(requestChannel="orders")
void placeOrder(Order order);
}]]></programlisting>
</para>
<para>
It is also possible to pass values to be interpreted as Message headers on the Message
that is created and sent to the request channel by using the @Header annotation:
<programlisting language="java"><![CDATA[ public interface FileWriter {
@Gateway(requestChannel="filesOut")
void write(byte[] content, @Header(FileHeaders.FILENAME) String filename);
}]]></programlisting>
</para>
</section>

3
spring-integration-reference/src/spring-integration-reference.xml
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@@ -58,9 +58,10 @@
<xi:include href="./splitter.xml"/>
<xi:include href="./aggregator.xml"/>
<xi:include href="./resequencer.xml"/>
<xi:include href="./delayer.xml"/>
<xi:include href="./chain.xml"/>
<xi:include href="./gateway.xml"/>
<xi:include href="./bridge.xml"/>
<xi:include href="./gateway.xml"/>
<xi:include href="./file.xml"/>
<xi:include href="./jms.xml"/>
<xi:include href="./ws.xml"/>